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(1)

Pursuant to Rule 416 promulgated under the Securities Act of 1933, as amended (the “Securities Act”), this Registration Statement shall also cover any additional ordinary shares of the Registrant that become issuable under the Prothena Corporation plc 2018 Long Term Incentive Plan (the “2018 Plan”) by reason of any share dividend, share split, recapitalization or other similar transaction effected without receipt of consideration that increases the number of outstanding shares of the Registrant’s ordinary shares.

(2)

Represents 8,282,461 ordinary shares available (or which may become available) for future grants under the 2018 Plan, which number consists of (a) 1,800,000 ordinary shares initially reserved for future grants under the 2018 Plan and (b) 6,482,461 ordinary shares available (or which may become available) for issuance under the 2018 Plan based on (i) the number of shares that were available under the Prothena Corporation plc Amended and Restated 2012 Long Term Incentive Plan (the “2012 Plan”) at the time of adoption of the 2018 Plan and (ii) shares subject to awards under the 2012 Plan that expire, are cancelled or otherwise terminate following the adoption of the 2018 Plan.

(3)	Estimated solely for the purpose of calculating the registration fee pursuant to Rules 457(c) and 457(h) of the Securities Act for the ordinary shares registered hereunder (based on the average of the high and low prices for the Registrant’s ordinary shares reported by The Nasdaq Stock Market on August 6, 2018).

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(a)	Registration Statement on Form 10 (File No. 001-35676) filed by the Registrant with the Commission under Section 12(b) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), on October 1, 2012, including the description of the Registrant’s ordinary shares contained therein, and any amendment or report filed for the purpose of updating such description;

(b)	Annual Report on Form 10-K for the year ended December 31, 2017, filed with the Commission on February 26, 2018;

(c)	The information specifically incorporated by reference into the Registrant’s Annual Report on Form 10-K for the year ended December 31, 2017 from the Registrant’s Definitive Proxy Statement on Schedule 14A, filed with the Commission on March 29, 2018;

(d)	Quarterly Report on Form 10-Q for the quarter ended March 31, 2018, filed with the Commission on May 9, 2018;

(e)	Quarterly Report on Form 10-Q for the quarter ended June 30, 2018, filed with the Commission on August 7, 2018; and

(f)	Current Reports on Form 8-K filed with the Commission on March 20, 2018 (other than Item 7.01 and Item 9.01), April 23, 2018, May 18, 2018, May 25, 2018, June 25, 2018 and July 26, 2018.

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“(1)	Subject to the provisions of this section, the following provision shall be void, namely, any provision:

(a)	purporting to exempt any officer of a company from; or

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(b)	purporting to indemnify such an officer against;

(2)	Subsection (1) applies whether the provision concerned is contained in the constitution of a company or a contract with a company or otherwise.

(3)	Notwithstanding subsection (1), a company may, in pursuance of any such provision as is mentioned in that subsection, indemnify any officer of the company against any liability incurred by him or her—

(a)	in defending proceedings, whether civil or criminal, in which judgment is given in his or her favour or in which he or she is acquitted; or

(b)	in connection with any proceedings or application referred to in, or under, section 233 or 234 in which relief is granted to him or her by the court.

(4)	Notwithstanding subsection (1), a company may purchase and maintain for any of its officers insurance in respect of any liability referred to in that subsection.

(5)	Notwithstanding any provision contained in any enactment, the constitution of a company or otherwise, a director may be counted in the quorum and may vote on any resolution to purchase or maintain any insurance under which the director might benefit

(6)	For the avoidance of doubt, if—

(a)	any business, trade or activity has been carried on by means of a company, or other body corporate, registered or formed under the laws of another country,

(b)	the period for which that business, trade or activity was so carried on was not less than 12 months preceding the date on which this subsection falls to be applied,

(c)	a provision of the kind referred to in subsection (1)(a) or (b) in relation to officers of the company or other body corporate was in being and valid under the laws of that country, and

(d)	a private company limited by shares is formed and registered to carry on that business, trade or activity,

(7)	Any directors’ and officers’ insurance purchased or maintained by a company before 6 April 2004 is as valid and effective as it would have been if this section had been in operation when that insurance was purchased or maintained.

(8)	In this section—

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(1)	Incorporated by reference to Exhibit 10.1 of the Registrant’s Current Report on Form 8-K filed with the Commission on May 18, 2018.

*	Indicates management contract or compensatory plan or arrangement.

a.	The undersigned Registrant hereby undertakes:

1.	To file, during any period in which offers or sales are being made pursuant to this Registration Statement, a post-effective amendment to this Registration Statement:

(i)	To include any prospectus required by Section 10(a)(3) of the Securities Act;

(ii)

To reflect in the prospectus any facts or events arising after the effective date of this Registration Statement (or the most recent post-effective amendment thereof) which, individually or in the aggregate, represent a fundamental change in the information set forth in this Registration Statement. Notwithstanding the foregoing, any increase or decrease in volume of securities offered (if the total dollar value of securities offered would not exceed that which was registered) and any deviation from the low or high end of the estimated maximum offering range may be reflected in the form of prospectus filed with the Commission pursuant to Rule 424(b) if, in the aggregate, the changes in volume and price represent no more than 20 percent change in the maximum aggregate offering price set forth in the “Calculation of Registration Fee” table in the effective registration statement;

(iii)	To include any material information with respect to the plan of distribution not previously disclosed in this Registration Statement or any material change to such information in this Registration Statement;

2.	That, for the purpose of determining any liability under the Securities Act, each such post-effective amendment shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

3.	To remove from registration by means of a post-effective amendment any of the securities being registered which remain unsold at the termination of the offering.

b.	The undersigned Registrant hereby undertakes that, for purposes of determining any liability under the Securities Act, each filing of the Registrant’s annual report pursuant to Sections 13(a) or 15(d) of the Exchange Act (and, where applicable, each filing of an employee benefit plan’s annual report pursuant to Section 15(d) of the Exchange

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h.

Insofar as indemnification for liabilities arising under the Securities Act may be permitted to directors, officers and controlling persons of the Registrant pursuant to the provisions described under “Item 6-Indemnification of Directors and Officers,” or otherwise, the registrant has been advised that in the opinion of the Commission such indemnification is against public policy as expressed in the Securities Act and is, therefore, unenforceable. In the event that a claim for indemnification against such liabilities (other than the payment by the Registrant of expenses incurred or paid by a director, officer or controlling person of the Registrant in the successful defense of any action, suit or proceeding) is asserted by such director, officer or controlling person in connection with the securities being registered, the Registrant will, unless in the opinion of its counsel the matter has been settled by controlling precedent, submit to a court of appropriate jurisdiction the question whether such indemnification by it is against public policy as expressed in the Securities Act and will be governed by the final adjudication of such issue.

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